<p>This rule allows the definition of custom rules using XPath expressions.</p>

<p>Issues are created depending on the return value of the XPath expression. If the XPath expression returns:</p>

<ul>
  <li> a single or list of AST nodes, then a line issue with the given message is created for each node
  </li><li> a boolean, then a file issue with the given message is created only if the boolean is true
</li><li> anything else, no issue is created
</li></ul>

<p>Here is an example of an XPath expression to log an issue on each if statement:</p>

<pre>
//IF_STATEMENT
</pre>

